Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
~:S~3~
-- 1 --
The present invention relates -to the thermal
stabilization oE halogeno-vinyl polymers and in particular
polyvinyl chloride. More particularly, the invention
relates to a process for the thermal stabilization of a
halogeno-vinyl resin, which process comprises lncorporating
into the polymer, a mixture additives which reduce the
harmful effects of heat on the polymer.
Current at-tempts to make halogeno-vinyl polymers
subject as little as possible to alteration due to thermal
effects constitute a permanent interest of the industries
which produce or utilize these materials. As regards
polyvinyl chloride, the most important of the products of
this type, it has been -the object of research in relation to
its thermal stabilization for more than 50 years; as its
manuEacture takes place in the hot, generally between 150
and 200C, decomposition reactions with the loss of HCl,
scission of the macromolecular chains and others reduce the
mechanical, rheological and electrical properties of the
product with discolouration which can rapidly a-t-tain a black
colour. Also, Eor half a century, various additives have
been utilized to reduce this troublesome process. Among
the first stabilizers were alkaline earth soaps and lead
compounds, par-ticularly the silicates. Other metal
derivatives were applied subsequen-tly; then s-tep-by-step,
stabilization was perEected by the addition of a second
compound or co-stabilizer, such as for example an epoxide,
phosphite, phenol anti-oxidant, organic thio-compound etc.
During the past decade, substantial progress has been made
by the use of systems comprising both a Cd salt and a Ba or
Ca salt; since 1970, more -than 80 products of this type have
been on the market, under various trade names, such as
"Advastab", "Ferro Mark", "Synpron", e-tc. (Modern Plastics
Encyclopaedia, 1970-1971, pages 870-875). However,
7~39
2.
1 the toxicity andh1gh cost of cadmium have led to a search
for other means, which has produced among others systems
of compounds of Ba with Zn or Ca with Zn, numerous
products now being on sale, also. On the other hand,
because good results have been obtained with organic Sn
and Sb derivatives, attempts have been made to improve these
and the addition of certain mercaptans has been found of
interest, as indicated in French Published Patent
Specification 2434835 and in German Patent Specification
1217609 or US Patent Specification 3063963. However, both
for health reasons and for cost reasons, the present
tendency is the replacement of heavy metals, both Cd as
well as Sn, by completely non-toxic and less costly
stabilizers. Thus, at the present time, a return to
15 alkaline earth and zinc systems is desired, by enhancing
their stabilizing action by other additives. A typical
example of such efforts is to be found in French published s
Patent Applica-tion 2492391 (1980) and European published
Patent Application 0022047 (1980), which relate to stabi-
20 lizers formed by Ca and Zn compounds, improved by means of
various thioglycolic esters; the second of these documen-ts
also refers to the addition of a polyol.
Since the additives, of whatever nature,
can only retard alterations due to heat and, if required,
25 also to visible light or other radiations, but without
completely suppressing the decomposition reactions, none
of the results obtained up to the present has been
regarded as definitive; all research can thus expect
chances to improve on the prior art.
The present invention results from research
effected according to the new tendency mentioned above and
it provides a clear improvement in the thermal resistance
of halogeno-vinyl resins~ The unexpected character of this
invention lies in the fact that the improvement in
stability is obtained more economicaliy and also with less
~.25,~39
-- 3
odour, by the addition to the resin of a mixture containing
mercapto-alkanoic acid esters of the mixed type, due to
reduction in the relative number of -S~l groups in the
molecule of such esters utilized according to the prior art.
The use of mercapto-esters in general, in
conjunction with stabilizing metal compounds and, in
particular, with polyol mercapto-alkanoic acid esters, is
known from French Patent Specification 2492391 and US Patent
3144422; the effect increases with the proportion of the
stabilizer in the resin and thus the conten-t of -S~l groups.
In a surprising way, the stabilization is at least as good
or even better, while providing a certain econorny, when, in
accordance with the invention, use is made of mercapto-
esters which contain less -SH groups with respect to their
alcohol residues and, consequently, less mercapto-groups per
100 parts of resin.
The advantages of the invention lie in that it
leads to plastics ma-terials which are as stable and as good
in quality as materials which include Cd or Sn compounds,
although i-t only utilizes additives which are less costly
and non-toxic. Also, plastics materials stabilized
according to the invention are free from any odour, in
contrast -to those which contain thioglycolic esters
according to the prior art; they have good resistance to
humidity and water due to the absence of the hydroxyl-
containing additives employed in the prior art mentioned
above.
The process according to the invention as claimed
hereinafter consists in incorporating into a halogeno-vinyl
resin a mixture of:
a) at least one polyol mercapto-alkanoic acid
ester of the mixed type, said mixed ester having one part
only of the hydroxyl groups of its polyol constituent
esterified by the mercapto alkonoic acid and all -the o-ther
.~ ,,
.~.,i
4 - ~
hydroxyl groups of its polyol constituent, or a par-t of said
other groups, esterified by a sulfur-free organic acid;
b) at least one stabilizing metal compound whose
metal is selected from groups IIB, IIIA, IVA, and VA of the
Periodic Classifica-tion of the Elements, and
c) at least one alkaline earth metal organic
compound.
Other stabilizers or additives known per se, may
also be used in the mixture incorporated -to the resins, such
10 as fatty compounds, preferably oxidized.
The process according to the inven-tion is
particularly effective in the case of plasticized resins.
Preferably, the metal of Groups IIB -to VA
mentioned above is zinc, but i-t can be selected from others.
15 As the alkaline earth metals, the ones most suitable are Ca,
Ba and/or Sr.
The mercapto--acid ester can carry, on the same
polyol residue, residues of several different acids
containing -SH groups and/or several acids without -SH
20 groups.
The mercapto-acids forming the mixed esters used
according to the invention can be represented generally by
the formula:
(HS)n-R-(COOH)m (1)
in which n has a value from 1 to 5, m = 1 or 2, R is a C1 to
C35 aliphatic chain or ring, optionally branched, preferably
from C2 to C17, which, for m = 1, correspond to the
respective total numbers of C2 to C3~ and C3 to C18.
By way of non-limitative example, various
mercapto-acid esters u-tilizable according to the invention
are set out below:
'~'
39
- 4a -
a - mercaptopropionic, 1-13C-CI~-C0211 (or 2-mercaptopropionic);
Sll
~ - mercaptopropionic HSCH2CH2 C02~1 (or 3-mercapto-
propi.onic);
w - mercaptoundecanoic HSCH2(CH2)9C0211, ( or ll-mercapto-
undecanoic)
.'
~`:
r~ ~39
5.
1 10 - mercaptoundecanoic H3C-CH(CH~)8C02H,
SH
mercaptosuccinic H02C-CH-CH2C02H (or thiomalic);
SH
dimercaptosuccinic HO2C-CH-CH-CO2H;
~ 5H ~H
2 - mercapto-benzoic, ~ CO2H (or thiosalicylic)
SH
As indicated above, a proportion of the -OH
groups of the polyol from which the mercapto-ester is
derived are esterified by another carboxylic acid, which
must not carry the -SH function. Such a carboxylic
acid, of the general formula R'(CO2H)p, is preferentially
a mono- or di-acid (p = 1 to 2). R' can be a straight or
branched aliphatic alkyl or alkenyl or aromatic group
containing at least 2 carbon atoms and, preferably, 5
to 37 and most preferably 5 to 17. While any carboxylic
acid can be utilized, those preferred are the fatty acids,
particularly caprylic, octanoic, cetanoic, pelargonic,
capric, undecanoic, lauric, myristic, palmitic, stearic,
isostearic, oleic, linoleic, linolenic, behenic and
montanic. Other particularly suitable acids are succinic,
adipic, glutaric, pimelic, suberic, azelaic, sebacic,
dioleic, malic, tartaric or phthalic, as well as aromatic
mono-acids, such as benzoic.
The polyol, from which the mixed mercapto-
ester utilized according to the invention is derived,
can be formed by a straight or branched carbon chain or
ring, generally from C2 to C30 but preferably from C2 to
C20, comprising a number of OH groups greater than or equal
to 2. Various other functions can also be present, in
particular ether oxide, thiol, sulphide, disulphide~
polysulphide, carboxylic acid, ester, amine. As non-
limitative examples of the polyols, the following materials
~257~39
6.
1 can be mentioned:
ethylene glycol and
polyethylene glycol Ho~CH2CH2OtrCH2CH2OH r = 1 to 30;
propylene glycol and polypropylene glycol HO~CH2-CH-Ots-CH2CH-OH s = 1 to 30; CH3 CH3 .
thiodiglycol, HOCH2CH2SCH2CH2OH ; pentaerythritol, C(CH2OH)4;
dipentaerythritol, (HOCH2)3C-CH2OCH2C(CH2OH)3 ; tripenta-
erythritol, (HOCH2)3CCH2OCH2C~CH2OH)2CH2OCH2C(CH2OH)3 ; tri-
methylolpropane, CH3CH2C(CH2OH)3 ; glycerol, HOCH2CH(OH)CH2OH;thioglycerol, HSCH2CH(OH)CH2OH or HOCH2CH(SH)CH2OH ; butane-
diol-1,2, butanediol-1,3 ; pentols, hexols and the like.
While a polyol residue constitutes a
necessary part of the mercapto-esters according to the
invention, they can also carry mono-alcohol residues; it
is in fact recommendable to decrease the molecular weight
of the ester when a polyacid is being used. In this case,
part of the carboxyl groups of the polyacid can advanta-
geously be esterified with a mono-alcohol; the latter is
generally from C1 to C20 and preferably from C2 to C8. This
precaution is useful particularly when the mercapto-ester
could have a molecular weight greater than 1200.
By way of non-limitative examples of the
mixed esters, reference can be made to :
Pentaerythrityl tris (3-mercapto-propionate)monocaprate
C(CH2OCCH2CH2SH)3 CH2OC,(CH2)8 3
O O
Pentaerythrityl mono (2-mercapto-propionate)triscaproate
C(cH2occH(sH)cH3~cH2oc(cH2)4cH373
O
Pentaerythrityl tris (3-mercapto-propionate~monostearate
35 17llOcH2c(cH2occH2cH2sH)3
O O
7.
1 Pentaerythrityl bis (3-mercapto-propionate)bispelargonate
(H17C8CIOCH2)C(CH2OClCH2CH2SH)2
O O
Trimethylpropane bis (3-mercaptopropionate)monooctanoate
H3ccH2c(cH2ollcH2c~2sH)2(cH2oll 7 15
O O
Ethylene-glycol 3-mercapto-propionate-laurate
HscH2cH2clocH2cH2olcl(cH2)lO 3
O O
Pentaerythrityl bis (thioglycolate)bispalmitate
CH2C CH2) 2C/CH20C(CH2) 14CH372
O O
Glyceryl bis (3-mercapto-propionate)mono-oleate
CH3OCCH2CH2SH
CHOC,IC 2 2
l O
CH20,C, -C17H33
Glyceryl bls(3-mercaptopropionate)monooctanoate
CH2Oç(cH2)6c 3
O CH20CCH2CH2SH
CHOCCH2CH2SH and/or CHOC(CH2)6CH3
l O l O
CH20CCH2CH2SH CH20CCH2CH2SH
O O
Thioglyceryl mono (3-mercapto-propionate)monooctanoate
CH2SH C,H2SH CH2OCCH2CH,SH
CHO2C(CH2)6C 3 and/or CHO2CH2CH2SH and/or CH-SH
CHo2ccH2cH2sH CHO2(CH2)6c 3 CH2Oc(cH2)6c 3
o
The fatty compound or compounds which can
advantageously be present in the composition of materials
stabilized according to the invention is/are in general
~'5~7~39
-- 8 --
C1 to C12 alkyl esters of ylycol and/or glycerol with one or
more C8 to C24 Eatty acids, preferably unsaturated, which
have undergone epoxidation. I-t is sui-table -to utilize for
this purpose a natural oil, such as linseed, soya or Eish
oil, which has been epoxidised.
The minimum molecular weigh-t oE the mixed
mercapto-ester is 178, corresponding to the lightest acids,
mercapto-acetic and acetic, and the lightest polyol,
ethylene glycol; this "rninimal" mixed ester is:
Hs-cil2coo-cH2cH2-oocH3
The preferred minimum is 206, corresponding to
ethylene 1-mercaptopropionate-2-propionate:
HS-CH2CH2COO-CH2CH2-OOC CH2 3
As regards a "heavy" ester, reference can be made
for example to a mixed fatty mercapto-ester of a sugar, in
particular glucose tris-Lmercatosteara-te~bis-stearate.
(~IS-C17 ~134coo~3 ~
~ C5H6CHO M=1608
(Cl7H3scOo)2
As regards the molecular weights of the mercapto-
esters utilized, they can range from 178 to abou-t 2000 and
preferably from 200 to 1000. Thus for example,
pentaerythrityl bis-(mercapto-propiona-te)bis-octanoate,
which gives excellent results, has a molecular weight oE
564.
The mixed ester used in the process of the
invention must have at least one of the -OH groups of its
polyol constituent es-terified by an organic acid not
3g
- 8a -
carrying an --S~-l group, while all or part of -the other -011
groups are esterified by a mercapto-acid. Conversely, mixed
esters in which the molecule carries a single mercapto-acid
are suitable for stabilization, where the o~her acid or
acids is/are free from -Sll. In the commonest case of esters
derived
~2~i7
9.
1 from polyols having 2 to 6 -O~ groups, there can be
respectively 1 mercapto-acid residue per 1 to 5 acid
residues without -S~ or reciprocally 1 non-mercapto-acid
residue per 1 to 5 mercapto-acid residues.
Among the organic compounds of alkaline earth
metals and various compounds of zinc, mention can be made
particularly of the carboxylates, mercaptides and ZnC12.
Among the carboxylates, mention can be made
in a non-limitative manner of the caproate, 2-ethyl-
hexanoate, octanoate, perlargonate, laurate, palmitate,
stearate, oleate, benzoate, phenate, alkyl-phenate, naph-
thenate and neoalkanoate. Among the mercaptides, reference
can be made to those derived from aliphatic mercaptans,
mercapto-acid esters or mercaptoalkyl esters.
However, a certain number of derivatives such
as the carbonate, oxide, hydroxide, sulphate, halide,
(chloride, bromide) can also be used advantageously.
The invention, which applies to various
halogeno-vinyl polymers and copolymers, particularly poly-
vinyl chloride, polyvinylidene chloride, polyvinylacetochloride and superchlorinated polyvinyl chloride and
chlorofluorovinyl resins etc, has, in particular, much
importance for plastics materials based on polyvinyl
chloride. As in the known art, the proportion of the
primary stabilizer, which here is an alkaline earth metal
organic compound jointly with a zinc organic compound,
is generally from 0.01 to 6% by weight and most preferably
from 0.05 to 3%, with respect to the resin to be stabilized.
When the mixed mercapto-ester according to the invention
is employed as a co-stabilizer, i-ts proportion is within
the same limits, without having to be equal to that of the
primary stabilizer.
The Process is applied to plasticized poly-
vinyl ch~o~ide containing an epoxidised oil, characterized
~z~ 9
- 9a -
in that, by weight of resin, 0,1 to 3% of a mixed mercapto-
ester is incorporated in conjunction with 0,005 to 1,5% of an
organic Ca, Mg, Ba compound and 0,005 to 2,5% of a Zn compound.
In the particular case of polyvinyl chloride
plasticized by the addition of a plasticizer constituted by an
~5~ r~ rl~
lt).
1 sehacate, azelate, phosphate or a polyester, the proportions
per 100 parts by weight of the resin are preferably:
5 to 70 parts of plasticiser,
1 to 10 parts of fatty compounds,
0.1 to 2 parts of the al~aline earth
metal organic compound,
0.05 to 1.5 parts of the Zn organic
compound,
0.1 to 3 parts of the mixed mercapto-
ester.
The ratio between the alkaline earth and
zinc compounds is preferably from 1 to 6 moles of the
first per 1 mole of the second. In the case of calci~,
the best ratio ranges from 1 to 4 atoms Ca per 1 Zn.
In the non-limitative Examples which follow,
samples of polyvinyl chloride stabilized with an additive
according to the invention are subjected to discolouration
tests on heating. For this, the various compositions are
kneaded for 5 minutes at 160C on a roller mixer. The
sheets obtained have a thickness of about 1 mm. The
thermal test per se is effected in a furnace of the "SIGMA"
type manufactured by METRASTAT SA. Its principle is based
upon evidence of the gradual change in the colour resulting
from the thermal decomposition of long test pieces, in the
Z5 form of strips 25 cm long, cut from the above-mentioned
sheets and exposed temporarily to heat in a furnace
maintained at a constant temperature~
Outside the thermal enclosure, the apparatus
comprises an electromechanical system ensuring the transfer
of a movable sample-carrying plate, leaving the furnace
at a predetermined constant speed; an electronic assembly
regulates the speed of the plate and also regulates the
temperature of the furnace.
The discolouration of the resin is observed
for a given furnace temperature and sample discharge
~5~3~
11 .
1 speed. For each test, the "stability time" is recorded,
which is the time at which the resin becomes black or
when the evolution of the yellow index is recorded. The
compositions subjected to the tests comprise:
100 parts by weight of polyvinyl chloride known
under the trade name "LACQVYI. S 111" having
index K=67, and
40 parts by weight of dioctyl phthalate,
(tr~ade name - PALATINOL AH) .
EXAMPLES 1 to 5
The tests fox thermal resistance are
effected at 190C, the speed of discharge of the samples
being regulated to 30 minutes.
In the results table below, the percentages
indicate the proportions of additives incorporated in the
samples, before passage through the furnace.
Example No 1 2 3 4 5
Pentaerythrityl tetrakis
(3-mercapto-propionate) ... 0 0.4% 0 0 0
20 Pentaerythrityl bis (3-
mercapto-propionat,e)
bis octanoate ... 0 0 0.4~ 0 0.4%
Epoxidised soya oil ... 0 0 0 4% 4%
Yellow index
after 2D minutes ...160 135127 155 90
The first conclusion given by these results
is that the mixed mercapto-ester of Example 3 (bis-bis),
despite its -SH content of only half that of the corres-
ponding tetrakis (Example 2), has an effectiveness at least
as good as the latter or even slightly better; the yellow
index is 127 as against 135. The use of this mixed compound
is thus more economical.
The second interesting result obtained from
Example 4 and 5 is that, in the presence of epoxidised soya
oil, the mixed mercapto-ester (Example 5) acts strongly
13~
12,
1 to reduce the yellow index from 150 to 90.
EXAMPLES 6 to 10
Association of a mixed mercapto-ester with
standard stabilizers based on metal compounds. Tests at
5 190C.
Example No. 6 7 3 9 10
-
Sample discharge speed, mn ......... 30 30 30 60 60
Zn octanoate % ..Ø08 0.08 0.08 0.08 0.08
Ba octanoate % ... - - - 0.80 0.80
10 Pentaerythrityl tetrakis
(3-mercapto-propionate) ... - 0.4
Pentaerythrityl bis (3-
mercapto-propionate)-bis
octanoate ... _ 0.4 _ 0,4
Stability time, mn ...15 18 18 43 53
As in the foregoing tests, the mixed mercapto-
ester (bis-bis) of Examples 8 and 10 proves to be more
effective than the mercapto-ester (tetrakis) of Example 7,
although it contains half the number of -SH groups of the
latter.
Association of the mixed compound with
standard Ba and Zn stabilizers (Examples 9 to 10), shows
an improvement in the stability of (53-43):43 = 23.2
which is very appreciable.
EXAMPLES 11 to l9
Operation is as in the foregoing Examples,
but a proportion of plasticizer, dioctyl phthalate, is
used which is 50 parts by weight per 100 parts of resin,
the latter containing 5% of epoxidised soya oil, 0.3%
of Ca stearate and 0.15% of Zn stearate. The stabilities
at 190C in minutes have been found by the addition of
various mercapto-esters.
39
13 .
1 EXAMPLE ADDITIVE Stahility
~ ~ constitution mn
11 Nil 160
12 0.5 Pentaerythrityl tetra
(3-mercapto-propionate) 203
13 1.0 " " 227
14 1.0 Pentaerythrityl bis
(3-mercapto-propionate)bis-
octanoate 226
1.0 Pentaerythrityl tetra (11-
mercapto-undecanoate) 225
16 1.0 Pentaerythrityl tris (11-
mercapto-undecanoate)
mono-undecanoate 226
15 171.0 Propyleneglycol bis-
mercapto-acetate 189
181.0 Propyleneglycol mercapto-
acetate-hexanoate 194
191.0 Ethyl ll-Mercapto-undecanoate 176
20These tests show the possibility of
increasing the stability by about 30% (from 160 to 226)
by using in conjunction a mixed mercapto-ester with a
standard stabilizer system which comprises an epoxidised
oil and Ca and Zn stearates.
The foregoing results confirm the surprising
advantage of the mixed mercapto ester over an ordinary
mercapto-ester. Thus Example 14 (mixed ester) gives a
result as good as that of Example 13, mercapto alone,
despite its lower -SH content. As the latter is less than
half that of the compound of Example 13, it would be
better to compare Example 14 with 12 which contains 0.5%
of the mercapto-ester; however the stability in th~s
case is 203 minutes as against 226 for the additive
according to the invention (Example 14).
The same conclusion can be drawn on the sub~ect
39
14.
1 of the respective Examples 15-16 and 17-18; it is to be
noted in passing that the mercapto-acetate of the prior
art (Example 17) gives an odour to the resin.
Example 19 shows that a mercapto-ester of a
mono- alcohol is less efficient than mercapto-esters of
polyols.
EXAMPLES 20 to 23
By applying the technique of the foregoing
Examples to the same composition of polyvinyl chloride
with 50% of dioctyl phthalate and 5~ of epoxidised soya
oil, the nature and proportions of the stabilizers have
been varied. Examples 20 to 22 show the use of Ca and Zn
compounds, while Example 23 utilizes stab.ilisers of the
prior art based on Cd and Ba, considered to be particularly
effective.
Example No 20 21 2~ 23
_
Stabilisers additive ~
Ca Laurate 0.6 - - -
Ca Stearate ~0.30 0-30
Zn Stearate 0.15 0.15 - -
Zn Mercaptide
Zn(scH2cH2coo~l C12H25)2 0.15
Cd Stearate
25 Ba Stearate - ~ , 1.50
Pentaerythrityl bis ~3-
mercapto-propionate)bis-
octanoate 0.501.0 0.2
Stability in minutes 241226 230 250
These results demonstrate that, due to the
addition of the mercapto-ester, a stabilization equivalent
to that provided by the known Cd, Ba system is attained;
plus the advantage of avoiding all toxicity due to heavy
metals together with a much lower cost.
i7~a39
I!L ~
15.
1 EX~MPLES 24 $o 26
.
The resin composition comprising, per
100 parts of polyvinyl chloride, 50 parts of dioctyl
phthalate and 5 parts of epoxidised soya oil is utilized
with; 0.6% of Ba laurate and
0.15% of Zn steaxate as standard stabilizers.
The furnace was regulated to 190 C with
a sample discharge speed of 180 minutes. The
following stabilities are found with each of the co-
stabilizers employed for 3 different concentrations of
the latter.
Example No % O 0.1 0.2 0.5
24 Pentaerythrityl bis
(3-mercapto-propionate)
bis-pelargonate 105 119 124 139
Pentaerythrityl bis
(3-mercapto-propionate)
bis-octanoate 105 117 131 153
26 Pentaerythrityl tetra (3-
mercapto-propionate) 105 108 122 131
_
Thus, with 0.5% of the co-stabilizer in
Example 24, there is an increase in stability of
139-105 = 34 or (34:105)100 = 32.3%
and in Example 25
153-105 = 48 or (48:105)100 = 45.7%
as against 131-105 = 26 or (26:105)100 = 24.8% only, with
the normal mercapto-ester of Example 26.
EXAMPLE 27
Examples 8 and 10 are repeated with ZnC12
in place oE Zn octanoate. In practice, the same results
are obtained.
EXAMPLES 28 and 29
As in the foregoing Examples, mixtures are
used of 100 parts of the same polyvinyl chloride with 50
~5
:16.
1 parts of dioctyl phthalate, 5 parts of epoxidised soya
oil, 0.6 part of Ba octanoate and 0.04 part of ZnC12.
Operating at 190C, the samples are
discharged in 180 minutes. Stability times found:
S Example 28 without other additive 84 mn
Example 29 + 1 part of pentaerythri~yl
bis(3-mercapto-propionate)-bis-
octanoate 137 mn
or an improvement of 60%.
EXAMPLE 30
Test on non-plasticized polyvinyl chloride
only containing pentaerythrityl bis(3 mercapto-propionate)-
bis-octanoate. The press was operated at 160C. The
yellow index found: 90 against 101 for a control without
additive.
